The groundwork for a successful dental restoration lies in the ability of the restoration to bond to the underlying tooth surface. One key to creating a successful bond between the tooth surface and a polymer based dental restoration is to create a strong bond at the hybrid layer between the collagen fibrils of the dentin and the dental polymer forming the restoration. In creating such a hybrid layer, acidic compositions, such as phosphoric acid etchants are used to expose the collagen fibers at the dentin-adhesive interface.
However, it has been reported that a degradation of the dentin-adhesive interface occurs over time due in large part to the hydrolytic activity of endogenous matrix metalloproteinases (“MMPs”). Carrilho et al, J. Dent. Res. 86(1):90-94 (2007). MMPs are zinc- and calcium-dependent proteolytic enzymes that are present within the intact dentin matrix, and which may be released from mineralized dentin matrix through acid-induced demineralization, such as through the use of etchants during preparation of the tooth surface during a dental restoration. Mazzoni et al., Biomaterials 27:4470-4476 (2006). In particular, it has been reported that specific MMPs, including MMP-2, MMP-8, and MMP-9 that exist within the dentin migrate into the hybrid layer and contribute to collagenolytic and gelatinolytic activity that results in the progressive reduction in resin-dentin bond strength, causing an ongoing weakening of the restoration nearly from the time the dental practitioner secures the restoration. Id.
As such, various known MMP inhibitors have been utilized, including the use of benzamidine HCl and chlorhexadine compositions in acid conditioners to wash tooth preparations and inhibit the hydrolytic activity of MMPs that may migrate into the hybrid layer. Further, the use of these MMP inhibitors in acid washes results in the clinical removal of the composition when the acid etchant is rinsed approximately 15 seconds after its application. Carrilho et al, J. Dent. Res. 86(1):90-94 (2007). Additionally, it is well known that the use of chlorhexadine can result in the staining of dental tissues, resulting in an unacceptable restoration. See, e.g., U.S. Pat. Nos. 5,385,728; 4,839,158. As such, an improved method and compositions for inhibiting the hydrolytic reactivity of MMPs in the hybrid layer would be greatly appreciated.